Display device and electronic apparatus

ABSTRACT

A display panel including pixels disposed on a substrate, where each of the pixels includes a light emitting element, and a capacitor. The capacitor of a first one of the pixels is partially overlapped, in a vertical direction, by respective pixel areas of two of the pixels. The anode of the capacitor of the first one of the pixels may be disposed closer to the substrate than a cathode of the capacitor, thereby reducing a parasitic capacitance between the capacitor and an anode of the light emitting element of one of the two pixels overlapping the capacitor.

This is a Continuation application of U.S. patent application Ser. No.12/654,090, filed Dec. 10, 2009 which in turn claims priority fromJapanese Application No.: 2009-003201 filed in the Japan Patent Officeon Jan. 9, 2009, the entire contents of which being incorporated hereinby reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Recently, in the field of display devices that perform image display,flat type display devices formed by disposing pixels (pixel circuits)including light emitting elements in a matrix form have been spreadingrapidly. As the flat type display devices, organic EL display devicesusing organic EL (electroluminescence) elements that utilize aphenomenon of light emission at the time of applying an electric field,for example, to an organic thin film have been developed andcommercialized.

2. Description of the Related Art

The organic EL display device has the following features. The organic ELelement can be driven by an application voltage of 10 V or less, andthus has low power consumption. In addition, since the organic ELelement is a self-luminous element, the organic EL display does not needa light source (back light) that may be essential to a liquid crystaldisplay device. In addition, the response speed of the organic ELelement is very high with response time of several microseconds, andaccordingly, no afterimage occurs at the time of displaying a motionpicture.

Similarly to the liquid crystal display device, a simple (passive)matrix type or an active matrix type may be used as a driving method ofthe organic EL display device. Recently, active matrix-type displaydevices in which an active element such as an insulated gate-type fieldeffect transistor (generally, TFT (thin film transistor)) is disposed ina pixel circuit have been actively developed.

It is generally known that the I-V characteristics (current-voltagecharacteristics) of the organic EL element degrade as time elapses(so-called degradation overtime). In addition, a threshold voltage Vthof a driving transistor or the mobility μ of a semiconductor thin filmthat configures a channel of the driving transistor (hereinafter,described as “mobility of a driving transistor”) changes over time ormay be different for each pixel due to a deviation in the manufacturingprocess thereof.

Accordingly, in order to maintain emission luminance of the organic ELelement to be constant without being affected by the above-describedfactors, a configuration in which a compensation function forcharacteristic variances in the organic EL element and correctionfunctions including a correction function for variances in the thresholdvoltage Vth of the driving transistor (hereinafter, described as“threshold value correction”) or a correction function for variances inthe mobility μ of the driving transistor are included in each pixelcircuit has been used (for example, see JP-A-2006-133542).

SUMMARY OF THE INVENTION

Here, in a pixel layout in related art, pixels are disposed such thatthe TFT layout area is asymmetric in accordance with the size (constant)of each pixel circuit. On the other hand, pixels corresponding to eachcolor of R (red), G (green), and B (blue) are disposed at a constantpitch. Thus, when the size of a constituent element of a specific pixelis larger than that of a different pixel so as to increase the layoutdensity thereof, a part of the constituent element having high layoutdensity is disposed in a space of a pixel having low layout density. Insuch a case, parasitic capacitance is generated between a sourceelectrode of a driving transistor of the different pixel and an upperelectrode of an auxiliary capacitor of the specific pixel. As a result,there is a problem in that the reference electric potential is affectedby the parasitic capacitance so as to decrease the luminance.

Therefore, there is a need for providing technology for preventingluminance changes due to formation of parasitic capacitance between anelectrode of an auxiliary capacitor of one pixel of adjacent pixels andan electrode of the other pixel.

According to an aspect of an exemplary illustration of the presentinvention, a display panel is provided, comprising a plurality of pixelsdisposed on a substrate. Each of the plurality of pixels may include alight emitting element, and a capacitor. The capacitor of a first one ofthe plurality of pixels may be partially overlapped, in a directionorthogonal to the substrate, by respective pixel areas of two of theplurality of pixels.

According to another aspect of the exemplary illustration of the presentinvention, the capacitor of the first one of the plurality of pixels maybe partially overlapped, in a direction orthogonal to the substrate, byrespective first electrodes of the light emitting elements of the two ofthe plurality of pixels.

According to another aspect of the exemplary illustration of the presentinvention, the respective first electrodes of the light emittingelements of the two of the plurality of pixels may be anode electrodes.

According to another aspect of the exemplary illustration of the presentinvention, the capacitor of the first one of the plurality of pixels maybe connected to a first electrode, which may be an anode electrode, ofthe light emitting element thereof.

According to another aspect of the exemplary illustration of the presentinvention, the capacitor of the first one of the plurality of pixels maynot be connected to a first electrode, which may be an anode electrode,of the light emitting element of any of the plurality of pixels otherthan the one of the plurality of pixels.

According to another aspect of the exemplary illustration of the presentinvention, the first one of the plurality of pixels may be also one ofthe two of the plurality of pixels whose respective pixel areas overlapthe capacitor of the first one of the plurality of pixels.

According to another aspect of the exemplary illustration of the presentinvention, a capacitance of the capacitor of the first one of theplurality of pixels may be different from a capacitance of the capacitorof at least one other of the plurality of pixels.

According to another aspect of the exemplary illustration of the presentinvention, the first one of the plurality of pixels may be a blue pixel.

According to another aspect of the exemplary illustration of the presentinvention, one of the two of the plurality of pixels whose respectivepixel areas overlap the capacitor of the first one of the plurality ofpixels may be a blue pixel.

According to another aspect of the exemplary illustration of the presentinvention, the other one of the two of the plurality of pixels whoserespective pixel areas overlap the capacitor of the first one of theplurality of pixels may be a green pixel.

According to another aspect of the exemplary illustration of the presentinvention, a capacitance of the capacitor of the blue pixel may belarger than a capacitance of the capacitor of the other one of the twoof the plurality of pixels whose respective pixel areas overlap thecapacitor of the first one of the plurality of pixels.

According to another aspect of the exemplary illustration of the presentinvention, each of the plurality of pixels may further include a drivingtransistor, which has a first current electrode connected to the lightemitting element and to the capacitor and which may be configured tosupply a drive current corresponding to a voltage between the firstcurrent electrode and a gate electrode thereof to the light emittingelement, and a sampling transistor configured to sample a video signal.Furthermore, for each of the plurality of pixels, a first electrode ofthe capacitor may be connected to a first electrode of the lightemitting element, which may be an anode electrode.

According to another aspect of the exemplary illustration of the presentinvention, for each of the plurality of pixels, a second electrode ofthe capacitor may be connected to the gate electrode of the drivingtransistor and the capacitor may be configured to store a potentialcorresponding to the video signal sampled by the sampling transistor.

According to another aspect of the exemplary illustration of the presentinvention, for each of the plurality of pixels, the first electrode ofthe capacitor may be disposed further from the first electrode of thelight emitting element than a second electrode of the capacitor.

According to another aspect of the exemplary illustration of the presentinvention, for each of the plurality of pixels, a second electrode ofthe capacitor may be connected to a second electrode of the lightemitting element, which may be a cathode electrode.

According to another aspect of the exemplary illustration of the presentinvention, the plurality of pixels may be grouped into color imageformation units, each comprising N≧3 ones of the plurality of pixelsthat each have a color different from that of the other pixels of theunit, each unit including at least a blue pixel, a green pixel, and ared pixel. Furthermore, the two of the plurality of pixels whoserespective pixel areas overlap the capacitor of the first one of theplurality of pixels may be grouped in the same unit as the first one ofthe plurality of pixels.

According to another aspect of the exemplary illustration of the presentinvention, the first one of the plurality of pixels may be a blue pixel.

According to another aspect of the exemplary illustration of the presentinvention, one of the two of the plurality of pixels whose respectivepixel areas overlap the capacitor of the first one of the plurality ofpixels may be a blue pixel.

According to an aspect of a second exemplary illustration of the presentinvention, a display panel may be manufactured by forming a plurality ofpixels on a substrate, wherein each of the plurality of pixels includesa light emitting element, and a capacitor. Furthermore, the capacitor ofa first one of the plurality of pixels may be at least partiallyoverlapped, in a direction orthogonal to the substrate, by respectivepixel areas of two of the plurality of pixels.

According to an aspect of a third exemplary illustration of the presentinvention, a display panel may be manufactured by providing a substrate;forming a plurality of pixel circuits on the substrate, each of theplurality of pixel circuits including a driving transistor, a samplingtransistor, and a capacitor; and forming a plurality of light emittingelements on the plurality of pixel circuits, the plurality of lightemitting elements being electrically connected to respective ones of theplurality of pixel circuits. Furthermore, an anode electrode of thecapacitor of one of the plurality of pixel circuits may be disposedcloser to the substrate than a cathode electrode of the capacitor of theone of the plurality of pixel circuits and a first one of the pluralityof light emitting elements and a second one of the plurality of lightemitting elements may be formed such that they both at least partiallyoverlap, in a direction orthogonal to the substrate, the capacitor ofthe one of the plurality of pixel circuits.

According to an aspect of a fourth exemplary illustration of the presentinvention, there may be provided a display device including: a pixelarray unit having pixels including a circuit configuration, in which afirst electrode of an electro-optical element and a source electrode ofa driving transistor may be connected together, a gate electrode of thedriving transistor and a source electrode or a drain electrode of awriting transistor may be connected together, a holding capacitor may beconnected between the gate electrode and the source electrode of thedriving transistor, and an auxiliary capacitor may be connected betweenthe first electrode and a second electrode of the electro-opticalelement, disposed on a substrate in a matrix shape. From one pixel ofadjacent pixels to an area of the other pixel, the auxiliary capacitorof the one pixel may be set to be disposed, and an electrode of theauxiliary capacitor that may be disposed on the electro-optical elementside may be conductive with the second electrode of the electro-opticalelement. The embodiment of the invention also provides an electronicapparatus that has the above-described display device disposed in a mainbody casing.

According to another aspect of the fourth exemplary illustration of thepresent invention, from one pixel of adjacent pixels to an area of theother pixel, the auxiliary capacitor of the one pixel may be set to bedisposed, and an electrode of the auxiliary capacitor that may bedisposed on the electro-optical element side may be conductive with thesecond electrode of the electro-optical element. In other words, anelectrode of the auxiliary capacitor, which may be disposed on the upperside, has a cathode electric potential, and the electrode having thecathode electric potential may be interposed between the anode electrodeof the other pixel and the electrode of the auxiliary capacitor of theone pixel that has the anode electric potential. A shield effect may beexhibited by the electrode having the cathode electric potential.

According to an aspect of a fifth exemplary illustration of the presentinvention, there may be provided a display device including: a pixelarray unit having pixels including a circuit configuration, in which afirst electrode of an electro-optical element and a source electrode ofa driving transistor may be connected together, a gate electrode of thedriving transistor and a source electrode or a drain electrode of awriting transistor may be connected together, a holding capacitor may beconnected between the gate electrode and the source electrode of thedriving transistor, and an auxiliary capacitor may be connected betweenthe first electrode and a second electrode of the electro-opticalelement, disposed on a substrate in a matrix shape. From one pixel ofadjacent pixels to an area of the other pixel, the auxiliary capacitorof the one pixel may be set to be disposed, and a shield electrode,which may be conductive with the second electrode of the electro-opticalelement, may be disposed between the auxiliary capacitor and the firstelectrode of the electro-optical element of the other pixel.

According to another aspect of the fifth exemplary illustration of thepresent invention, between the electrode of the electrodes of theauxiliary capacitor of one pixel of adjacent pixels that may be disposedon the electro-optical element side and the anode electrode of the otherpixel can be shielded by the shield electrode that may be conductivewith the cathode electrode.

According to the exemplary illustrations of the present invention, in acircuit configuring a pixel, luminance changes due to formation ofparasitic capacitance between an electrode of an auxiliary capacitor ofone pixel of adjacent pixels and an electrode of the other pixel can beprevented.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a system configuration that representsan active-matrix type organic EL display device that serves as a premiseof an embodiment of the present invention.

FIG. 2 is a circuit diagram representing a concrete example of theconfiguration of a pixel (pixel circuit).

FIG. 3 is a timing waveform chart for illustrating the operation of anorganic EL display device of the active matrix type that serves as apremise of an embodiment of the invention.

FIGS. 4A to 4D are explanatory diagrams (first example) illustrating thecircuit operation of an organic EL display device of the active matrixtype that serves as a premise of an embodiment of the invention.

FIGS. 5A to 5D are explanatory diagrams (second example) illustratingthe circuit operation of an organic EL display device of the activematrix type that serves as a premise of an embodiment of the invention.

FIGS. 6A to 6C are explanatory diagrams (third example) illustrating thecircuit operation of an organic EL display device of the active matrixtype that serves as a premise of an embodiment of the invention.

FIG. 7 is a circuit diagram representing a pixel structure in relatedart.

FIG. 8 is a schematic plan view illustrating a pixel structure inrelated art.

FIG. 9 is a schematic plan view illustrating the pixel structure thatsolves a problem in the pattern density.

FIG. 10 is a schematic plan view of a layout that is acquired by addinganode electrodes to the layout represented in FIG. 9.

FIG. 11 is a cross-sectional view taken along line A-A shown in FIG. 10.

FIG. 12 is a circuit diagram illustrating parasitic capacitance.

FIGS. 13A and 13B are timing charts illustrating the operation performedduring a sampling period of a video signal and a mobility correctingperiod.

FIG. 14 is a diagram of the system configuration representing oneexample of this embodiment.

FIG. 15 is a schematic plan view illustrating an example (first example)of a pixel structure according to this embodiment.

FIG. 16 is a cross-sectional view taken along line B-B shown in FIG. 15.

FIG. 17 is a cross-sectional view taken along line C-C shown in FIG. 15.

FIG. 18 is a schematic cross-sectional view illustrating an example(second example) of a pixel structure according to this embodiment.

FIG. 19 is a perspective view showing the outer appearance of atelevision set to which this embodiment is applied.

FIGS. 20A and 20B are perspective views showing the outer appearance ofa digital camera to which this embodiment is applied. FIG. 20A is aperspective view viewed from the front side, and FIG. 20B is aperspective view viewed from the rear side.

FIG. 21 is a perspective view showing the outer appearance of a notebookpersonal computer to which this embodiment is applied.

FIG. 22 is a perspective view showing the outer appearance of a videocamera to which this embodiment is applied.

FIGS. 23A to 23G are diagrams showing the outer appearances of acellular phone, to which this embodiment is applied. FIG. 23A is a frontview in an open state, FIG. 23B is a side view thereof, FIG. 23C is afront view in a closed state, FIG. 23D is a left side view, FIG. 23E isa right side view, FIG. 23F is a top view, and FIG. 23G is a bottomview.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, an embodiment of the present invention (hereinafter,referred to as an “embodiment”) will be described. The descriptionthereof will be followed in the following order.

1. Display Device (System Configuration, Pixel Circuit, and CircuitOperation) As Premise of This Embodiment

2. Problem in Pixel Structure in Related Art (Pixel Circuit, Layout,Circuit Diagram Configuring Parasitic Capacitance, and Timing Chart)

3. Configuration Example According To This Embodiment (SystemConfiguration and Example of Wiring Structure)

4. Applications (Various Applications to Electronic Apparatuses)

1. Display Device (System Configuration, Pixel Circuit, and CircuitOperation) as Premise of this Embodiment System Configuration

FIG. 1 is a schematic diagram of a system configuration that representsan active-matrix type display device that is a premise of thisembodiment.

Here, as an example, an organic EL display device of an active-matrixtype that uses an electro-optical element of a current-driven type ofwhich emission luminance changes in accordance with the value of acurrent flowing through the device such as an organic EL element(organic electroluminescence element) as a light emitting element of apixel (pixel circuit) will be described.

As represented in FIG. 1, an organic EL display device 100 has aconfiguration including a pixel array unit 102 formed bytwo-dimensionally disposing pixels (PXLC) 101 in a matrix shape and adriving unit that is disposed on the periphery of the pixel array unit102 and drives each pixel 101. As the driving unit that drives thepixels 101, for example, a horizontal driving circuit 103, a writingscanning circuit 104, and a power supply scanning circuit 105 aredisposed.

In the pixel array unit 102, in the pixel array of m rows and n columns,scanning lines WSL-1 to WSL-m and power supply lines DSL-1 to DSL-m arewired for each pixel row, and signal lines DTL-1 to DTL-n are wired foreach pixel column.

The pixel array unit 102, generally, is formed on a transparentinsulating substrate such as a glass substrate and has a flat-type panelstructure. Each pixel 101 of the pixel array unit 102 may be formed byan amorphous silicon TFT (thin film transistor) or a low-temperaturepoly silicon TFT. When the low-temperature polysilicon TFT is used, thehorizontal driving circuit 103, the writing scanning circuit 104, andthe power supply scanning circuit 105 can also be mounted on a displaypanel (substrate) that forms the pixel array unit 102.

The writing scanning circuit 104 is configured by a shift register thatsequentially shifts (transmits) start pulses sp in synchronization witha clock pulse ck or the like. The writing scanning circuit 104 suppliespulses (scanning signals) WS1 to WSm by sequentially writing the pulsesinto the scanning lines WSL-1 to WSL-m when a video signal is writteninto each pixel 101 of the pixel array unit 102, whereby sequentiallyscanning (line sequential scanning) the pixels 101 of the pixel arrayunit 102 in units of one row.

The power supply scanning circuit 105 is configured by a shift registerthat sequentially shifts the start pulses sp in synchronization with theclock pulse ck or the like. The power supply scanning circuit 105selectively supplies power supply line electric potentials DS1 to DSmthat are shifted between a first electric potential Vcc_H and a secondelectric potential Vcc_L lower than the first electric potential Vcc_Hto the power supply lines DSL-1 to DSL-m in synchronization with linesequential scanning performed by the writing scanning circuit 104.Accordingly, the power supply scanning circuit 105 controls emission ornon-emission of the pixels 101.

The horizontal driving circuit 103 appropriately selects either a signalvoltage Vsig of a video signal (hereinafter, it may be also referred toas only a “signal voltage”) corresponding to luminance information thatis supplied from a signal supply source (not shown) or a signal linereference electric potential Vo so as to be written into the pixels 101of the pixel array unit 102 through the signal lines DTL-1 to DTL-n, forexample, in units of one row. In other words, the horizontal drivingcircuit 103 employs a driving form of the line sequential writing typein which a signal voltage Vin of a video signal is written in units ofone row (line).

Here, the signal line reference electric potential Vo is a voltage (forexample, a voltage corresponding to a black level) that becomes areference for the signal voltage Vin of the video signal. In addition,the second electric potential Vcc_L is set to an electric potential thatis lower than the signal line reference electric potential Vo, forexample, an electric potential that is lower than “Vo−Vth” wherein athreshold voltage of a driving transistor is denoted by Vth. Morepreferably, the second voltage Vcc_L is set to an electric potentialthat is sufficiently lower than “Vo−Vth”.

Pixel Circuit

FIG. 2 is a circuit diagram representing a concrete example of theconfiguration of the pixel (pixel circuit).

As shown in FIG. 2, the pixel 101 has a pixel configuration in which anelectro-optical element of the current-driven type, in which theemission luminance changes in accordance with the value of a currentflowing through the device, for example, an organic EL element 1D isincluded as a light emitting element, and a driving transistor 1B, awriting transistor 1A, and a holding capacitor 1C are included inaddition to the organic EL element 1D. In other words, the pixel 101 hasa 2Tr/1C pixel configuration that is configured by two transistors (Tr)and one capacitor (C).

In the pixel 101 having such a configuration, N-channel TFTs are used asthe driving transistor 1B and the writing transistor 1A. However, thecombination of conductive types of the driving transistor 1B and thewriting transistor 1A described here is merely an example, and anembodiment of the invention is not limited to such a combination.

The organic EL element 1D has a cathode electrode connected to a commonpower supply line 1H that is wired commonly to all the pixels 101. Thedriving transistor 1B has a source electrode connected to the anodeelectrode of the organic EL element 1D and a drain electrode connectedto the power supply lines DSL (DSL-1 to DSL-m).

The writing transistor 1A has a gate electrode connected to the scanningline WSL (WSL-1 to WSL-m), one electrode (a source electrode or a drainelectrode) connected to the signal line DTL (DTL-1 to DTL-n), and theother electrode (the drain electrode or the source electrode) connectedto the gate electrode of the driving transistor 1B.

The holding capacitor 1C has one electrode connected to the gateelectrode of the driving transistor 1B and the other electrode connectedto the source electrode of the driving transistor 1B (the anodeelectrode of the organic EL element 1D). In addition, an auxiliarycapacitor 1J has one electrode connected to the anode electrode of theorganic EL element 1D and the other electrode connected to the cathodeelectrode of the organic EL element 1D.

In the pixel 101 having the 2Tr/1C pixel configuration, the writingtransistor 1A is in a conducting state in response to a scanning signalWS applied to the gate electrode from the writing scanning circuit 104through the scanning line WSL. Accordingly, the writing transistor 1Asamples a signal voltage Vin of a video signal corresponding to theluminance information supplied from the horizontal driving circuit 103or the signal line reference electric potential Vo through the signalline DTL so as to be written into the pixel 101.

The written signal voltage Vin or the signal line reference electricpotential Vo is applied to the gate electrode of the driving transistor1B, and is maintained in the holding capacitor 1C. When the electricpotential DS of the power supply line DSL (DSL-1 to DSL-m) is the firstpotential Vcc_H, the driving transistor 1B is supplied with a currentfrom the power supply line DSL and supplies a driving current having acurrent value corresponding to the voltage value of the signal voltageVin maintained in the holding capacitor 1C to the organic EL element 1D,whereby driving the organic EL element 1D by the current so as to emitlight.

Circuit Operation of Organic EL Display Device

Next, the circuit operation of the organic EL display device 100 havingthe above-described configuration will be described based on a timingwaveform chart represented in FIG. 3 with reference to operationexplanatory diagrams represented in FIGS. 4A to 6C. Incidentally, in theoperation explanatory diagrams represented in FIGS. 4A to 6C, thewriting transistor 1A is denoted by the symbol of a switch in order tosimplify the drawings. In addition, since the organic EL element 1D hasa capacitance component, an EL capacitance 1I is also shown in thediagrams.

The timing waveform chart represented in FIG. 3 shows changes in theelectric potential (writing pulse) WS of the scanning line WSL (WSL-1 toWSL-m), changes in the electric potential DS (Vcc_H and Vcc_L) of thepower supply line DSL (DSL-1 to DSL-m), and changes in the gate electricpotential Vg and the source electric potential Vs of the drivingtransistor 1B.

Emission Period

The organic EL element 1D is in a light emitting state before time t1 inthe timing waveform chart of FIG. 3 (emission period). During thisemission period, the electric potential DS of the power supply line DSLis the first electric potential Vcc_H, and the writing transistor 1A isin a non-conducting state.

At this moment, since the driving transistor 1B is set to operate in asaturation region, as shown in FIG. 4A, a driving current(drain-to-source current) Ids corresponding to the gate-to-sourcevoltage Vgs of the driving transistor 1B is supplied from the powersupply line DSL through the driving transistor 1B to the organic ELelement 1D. Accordingly, the organic EL element 1D emits light at aluminance level corresponding to the value of the current of the drivingcurrent Ids.

Threshold Value Correction Preparatory Period

Then, a new field of line-sequential scanning begins at time t1. Thus,as shown in FIG. 4B, the electric potential DS of the power supply lineDSL changes from the first electric potential (hereinafter referred toas a “high electric potential”) Vcc_to the second electric potential(hereinafter, referred to as a “low electric potential”) Vcc_L that issufficiently lower than the signal line reference voltage Vo-Vth of thesignal line DTL.

Here, letting Vel be the threshold voltage of the organic EL element 1Dand Vcath be the electric potential of the common power supply line 1H,when the low electric potential Vcc_L satisfies the relation ofVcc_L<Vel+Vcath, the source electric potential Vs of the drivingtransistor 1B is substantially equal to the low electric potentialVcc_L, and thus the organic EL element 1D is set to be in areverse-biased state and quenched.

Next, at time t2, as the electric potential WS of the scanning line WSLmakes a transition from a low electric potential side to a high electricpotential side, as shown in FIG. 4C, the writing transistor 1A is set ina conducting state. At this moment, since the signal line referenceelectric potential Vo is supplied from the horizontal driving circuit103 to the signal line DTL, the gate electric potential Vg of thedriving transistor 1B becomes the signal line reference electricpotential Vo. The source electric potential Vs of the driving transistor1B is the electric potential Vcc_L that is sufficiently lower than thesignal line reference electric potential Vo.

At this moment, the gate-to-source voltage Vgs of the driving transistor1B is Vo-Vcc_L. Here, when Vo-Vcc_L is not higher than the thresholdvoltage Vth of the driving transistor 1B, a threshold value correctingoperation to be described later may not be performed. Accordingly, theelectric potential relation may need to be set such that Vo-Vcc_L>Vth.As described above, an initialization operation of respectively fixing(determining) the gate electric potential Vg and the source electricpotential Vs of the driving transistor 1B to the signal line referenceelectric potential Vo and the low electric potential Vcc_L is athreshold value correction preparatory operation.

Threshold Value Correcting Period for First Time

Next, as shown in FIG. 4D, when the electric potential DS of the powersupply line DSL shifts from the low electric potential Vcc_L to the highelectric potential Vcc_H at time t3, the source electric potential Vs ofthe driving transistor 1B starts to rise, and a threshold valuecorrecting period for the first time starts. During the threshold valuecorrecting period for the first time, the source electric potential Vsof the driving transistor 1B rises. Accordingly, the gate-to-sourcevoltage Vgs of the driving transistor 1B becomes a predeterminedelectric potential Vx1, and the electric potential Vx1 is maintained atthe holding capacitor 1C.

Subsequently, at time t4 that is start of a latter part of thehorizontal period (1H), as shown in FIG. 5A, the signal voltage Vin ofthe video signal is supplied to the signal line DTL from the horizontaldriving circuit 103, whereby the electric potential of the signal lineDTL makes a transition from the signal line reference electric potentialVo to the signal voltage Vin. During this period, writing signalvoltages Vin into pixels of another row is performed.

At this moment, in order not to write the signal voltage Vin into pixelsof the current row, the electric potential WS of the scanning line WSLis allowed to make a transition from the high electric potential side tothe low electric potential side, whereby the writing transistor 1A is tobe in a non-conducting state. Accordingly, the gate electrode of thedriving transistor 1B is cut off from the signal line DTL to be in afloating state.

Here, when the gate electrode of the driving transistor 1B is in thefloating state, the holding capacitor 1C is connected between the gateand the source of the driving transistor 1B. Thus, when the sourceelectric potential Vs of the driving transistor 1B changes, the gateelectric potential Vg of the driving transistor 1B also changes inaccordance (follow) with the change in the source electric potential Vs.This is a bootstrap operation that is performed by the holding capacitor1C.

Also after time t4, the source electric potential Vs of the drivingtransistor 1B continues to rise so as to rise by Va1 (Vs=Vo−Vx1+Va1). Atthis moment, the gate electric potential Vg also rises by Va1 inaccordance with the rise in the source electric potential Vs of thedriving transistor 1B by the bootstrap operation (Vg=Vo+Va1).

Threshold Value Correcting Period for Second Time

When the next horizontal period begins at time t5, as shown in FIG. 5B,the electric potential WS of the scanning line WSL shifts from the lowelectric potential side to the high electric potential side, and thewriting transistor 1A is in the conducting state. Simultaneously, thesignal line reference electric potential Vo instead of the signalvoltage Vin is supplied to the signal line DTL from the horizontaldriving circuit 103, and a threshold value correcting period for thesecond time begins.

During the threshold value correcting period for the second time, thewriting transistor 1A is in the conducting state, and thus the signalline reference electric potential Vo is written. Accordingly, the gateelectric potential Vg of the driving transistor 1B is initialized backto the signal line reference electric potential Vo. The source electricpotential Vs drops in accordance with a drop in the gate electricpotential Vg at that moment. Then, again, the source electric potentialVs of the driving transistor 1B starts to rise.

Then, as the source electric potential Vs of the driving transistor 1Brises during the threshold value correcting period for the second time,the gate-to-source voltage Vgs of the driving transistor 1B becomes apredetermined electric potential Vx2, and this electric potential Vx2 ismaintained in the holding capacitor 1C.

Subsequently, at time t6 when a latter part of this horizontal periodbegins, as shown in FIG. 5C, as the signal voltage Vin of the videosignal is supplied from the horizontal driving circuit 103 to the signalline DTL, the electric potential of the signal line DTL is allowed tomake a transition from the offset voltage Vo to the signal voltage Vin.During this period, the signal voltage Vin is written into pixels ofanother row (the next row of the row being written at the previoustime).

At this moment, in order not to perform writing the signal voltage Vininto the pixels of the current row, the electric potential WS of thescanning line WSL is allowed to make a transition from the high electricpotential side to the low electric potential side, whereby the writingtransistor 1A is in the non-conducting state. Accordingly, the gateelectrode of the driving transistor 1B is cut off from the signal lineDTL to be in a floating state.

Also after time t6, the source electric potential Vs of the drivingtransistor 1B continues to rise so as to rise by Va2 (Vs=Vo−Vx1+Va2). Atthis moment, by the bootstrap operation, the gate electric potential Vgrises by Va2 in accordance with a rise in the source electric potentialVs of the driving transistor 1B (Vg=Vo+Va2).

Threshold Value Correcting Period for Third Time

The next horizontal period begins at time t7, and, as shown in FIG. 5D,the electric potential WS of the scanning line WSL is allowed to make atransition from the low electric potential side to the high electricpotential side, whereby the writing transistor 1A is in the conductingstate. Simultaneously, the signal line reference electric potential Voinstead of the signal voltage Vin is supplied to the signal line DTLfrom the horizontal driving circuit 103, and a threshold valuecorrecting period for the third time begins.

During this threshold value correcting period for the third time, as thewriting transistor 1A is in the conducting state, the signal linereference electric potential Vo is written. Accordingly, the gateelectric potential Vg of the driving transistor 1B is reinitialized tothe signal line reference electric potential Vo. In accordance with adrop in the gate electric potential Vg at that moment, the sourceelectric potential Vs drops. Then, the source electric potential Vs ofthe driving transistor 1B starts to rise again.

As the source electric potential Vs of the driving transistor 1B rises,finally, the gate-to-source voltage Vgs of the driving transistor 1Bconverges at the threshold voltage Vth of the driving transistor 1B,whereby a voltage corresponding to the threshold voltage Vth ismaintained in the holding capacitor 1C.

By performing the above-described threshold value correcting operationsfor three times, the threshold voltage Vth of the driving transistor 1Bof each pixel is detected, and a voltage corresponding to the thresholdvoltage Vth is maintained in the holding capacitor 1C. In addition,during the threshold value correcting period for the three times, inorder to allow a current to flow not to the organic EL element 1D sidebut only to the holding capacitor 1C side, the electric potential Vcathof the common power supply line 1H is set such that the organic ELelement 1D is in the cut-off state.

Signal Writing Period and Mobility Correcting Period

Next, at time t8, as the electric potential WS of the scanning line WSLis allowed to make a transition to the low electric potential side, asshown in FIG. 6A, the writing transistor 1A is in the non-conductingstate. Simultaneously, the electric potential of the signal line DTL isshifted from the offset voltage Vo to the signal voltage Vin of thevideo signal.

As the writing transistor 1A is in the non-conducting state, the gateelectrode of the driving transistor 1B is in a floating state. However,since the gate-to-source voltage Vgs is equal to the threshold voltageVth of the driving transistor 1B, the driving transistor 1B is in thecut-off state. Accordingly, a drain-to-source current Ids does not flowin the driving transistor 1B.

Subsequently, at time t9, as the electric potential WS of the scanningline WSL is allowed to make a transition to the high electric potentialside, as shown in FIG. 6B, the writing transistor 1A is in theconducting state. Thus, the signal voltage Vin of the video signal issampled so as to be written into the pixel 101. By writing the signalvoltage Vin by using the writing transistor 1A, the gate electricpotential Vg of the driving transistor 1B becomes the signal voltageVin.

Then, when the driving transistor 1B is driven in accordance with thesignal voltage Vin of the video signal, the threshold voltage Vth of thedriving transistor 1B is offset by the threshold voltage Vth maintainedin the holding capacitor 1C, whereby the threshold value correction isperformed.

At this moment, since the organic EL element 1D is in the first cutoffstate (high impedance state), a current (drain-to-source current Ids)flowing from the power supply line DSL to the driving transistor 1B inaccordance with the signal voltage Vin of the video signal flows in theEL capacitance 1I of the organic EL element 1D, whereby charging of theEL capacitance 1I is started.

By charging the EL capacitance 1I, the source electric potential Vs ofthe driving transistor 1B rises over time. At this moment, since thedeviation of the threshold voltage Vth of the driving transistor 1B hasbeen already corrected (corrected for the threshold value), thedrain-to-source current Ids of the driving transistor 1B depends on themobility μ of the driving transistor 1B.

Finally, when the source electric potential Vs of the driving transistor1B rises up to the electric potential of “Vo−Vth+ΔV”, the gate-to-sourcevoltage Vgs of the driving transistor 1B becomes “Vin+Vth−ΔV”. In otherwords, an increase amount ΔV of the source electric potential Vs acts tobe subtracted from the voltage (Vin+Vth−ΔV) maintained in the holdingcapacitor 1C, that is, to discharge electric charges charged in theholding capacitor 1C for applying a negative feedback. Accordingly, theincrease amount ΔV of the source electric potential Vs becomes thefeedback amount of the negative feedback.

As described above, by applying the drain-to-source current Ids flowingthrough the driving transistor 1B to the gate input of the drivingtransistor 1B, that is, the gate-to-source voltage Vgs as a negativefeedback, mobility correction, in which the dependence of thedrain-to-source current Ids of the driving transistor 1B on the mobilityμ is eliminated, in other words, the deviation of the mobility μ foreach pixel is corrected, is performed.

In particular, the higher the signal voltage Vin of the video signal is,the larger the drain-to-source current Ids becomes, and thus theabsolute value of the feedback amount (correction amount) ΔV of thenegative feedback is increased. Accordingly, the mobility correction isperformed in accordance with the emission luminance level. In addition,when the signal voltage Vin of the video signal is constant, theabsolute value of the feedback amount ΔV for the negative feedback isincreased as the mobility μ of the driving transistor 1B is higher.Accordingly, the deviation of the mobility μ for each pixel can beeliminated.

Emission Period

Next, at time t10, as the electric potential WS of the scanning line WSLmakes a transition to the low electric potential side as shown in FIG.6C, the writing transistor 1A is in a non-conducting state. Accordingly,the gate electrode of the driving transistor 1B is cut off from thesignal line DTL so as to be in a floating state.

As the gate electrode of the driving transistor 1B is in the floatingstate, and simultaneously, the drain-to-source current Ids of thedriving transistor 1B starts to flow through the organic EL element 1D,the anode electric potential of the organic EL element 1D rises inaccordance with the drain-to-source current Ids of the drivingtransistor 1B.

The rise in the anode electric potential of the organic EL element 1D isnot different from a rise in the source electric potential Vs of thedriving transistor 1B. As the source electric potential Vs of thedriving transistor 1B rises, the gate electric potential Vg of thedriving transistor 1B also rises by the bootstrap operation of theholding capacitor 1C.

At this time, assuming that a bootstrap gain is one (ideal value), theamount of the rise in the gate electric potential Vg is equal to that inthe source electric potential Vs. Thus the gate-to-source voltage Vgs ofthe driving transistor 1B is maintained to be constant at Vin+Vth−ΔVduring the emission period. Then, at time t11, the electric potential ofthe signal line DTL shifts from the signal voltage Vin of the videosignal to the signal line reference electric potential Vo.

As is apparent from the description of the operation as above, in thisexample, the threshold value correcting period is set to be over a totalof 3 H periods including a 1 H period, in which signal writing andmobility correction are performed, and 2 H periods that precedes the 1 Hperiod. Accordingly, a sufficient time can be acquired as the thresholdvalue correcting period. Therefore, the threshold voltage Vth of thedriving transistor 1B can be correctly detected and maintained in theholding capacitor 1C, whereby the threshold value correcting operationcan be assuredly performed.

Here, the threshold value correcting period is set over the 3 H periods.However, this is only an example. Thus, as long as a sufficient time canbe acquired by a 1 H period, in which signal writing and mobilitycorrection are performed, as the threshold value correcting period, thethreshold value correcting period may not need to be set over thepreceding horizontal periods. On the other hand, when it is difficult toacquire a sufficient time by setting the threshold value correctingperiod to be over 3 H periods in a case where a 1H period is shortenedin accordance with an increase in the precision, the threshold valuecorrecting period may be set over 4 H periods or more.

2. Problem in Pixel Structure in Related Art Pixel Circuit

FIG. 7 is a circuit diagram representing a pixel structure in relatedart. A pixel 101 includes an organic EL element 1D, a driving transistor1B, a writing transistor 1A, a holding capacitor 1C, and an auxiliarycapacitor 1J.

More specifically, the anode electrode of the organic EL element 1D andthe source electrode of the driving transistor 1B are connectedtogether, and the gate electrode of the driving transistor 1B and thesource electrode or the drain electrode of the writing transistor 1A areconnected together. In addition, the holding capacitor 1C is connectedbetween the gate and the source electrode of the driving transistor 1B.In addition, the auxiliary capacitor 1J is connected between the anodeelectrode and the cathode electrode of the organic EL element 1D. Inaddition, parasitic capacitance 1I is formed in the organic EL element1D.

A signal line DTL is connected to the drain electrode or the sourceelectrode of the writing transistor 1A. In addition, to the gateelectrode of the writing transistor 1A, a scanning line WSL isconnected, and a predetermined timing is given. A power supply line DSLis connected to the drain electrode of the driving transistor 1B.

Layout of Pixel Circuit

FIG. 8 is a schematic plan view illustrating a pixel structure inrelated art. FIG. 8 represents the disposition configuration of an R(red) pixel, a G (green) pixel, and a B (blue) pixel. Each pixel isconfigured between the power supply line DSL and the scanning line WSLthat extend in the horizontal direction (horizontal direction in thefigure), and areas of the RGB pixels are partitioned by signal lines DTLthat extend in the vertical direction (the vertical direction in thefigure).

Within the area of each pixel, a writing transistor 1A, a drivingtransistor 1B, and a holding capacitor 1C are disposed. In addition, anauxiliary capacitor 1J that is used for adjusting writing gain ormobility correcting time is also disposed.

In the example represented in FIG. 8, a case is shown where the patterndensity of the G (green) pixel is lower than that of the R (red) pixel,and the pattern density of the B (blue) pixel is higher than that of theR (red) pixel. In a pixel having a high pattern density, wiring intervalis short, whereby a defective pattern or the like may be easilygenerated.

FIG. 9 is a schematic plan view illustrating the pixel structure thatsolves the problem in the pattern density. In this layout, the B (blue)pixel having a high pixel density is disposed so as to be reversed inthe horizontal direction with respect to the layout represented in FIG.8. Accordingly, in an area between the B (blue) pixel and the G (green)pixel, a signal line ETL-B is not disposed, and the auxiliary capacitor1J of the B (blue) pixel is set in from the above-described area to thearea of the G (green) pixel.

FIG. 10 is a schematic plan view of a layout that is acquired by addinganode electrodes to the layout represented in FIG. 9. The anodeelectrode AD is denoted by a thick solid line in the figure and isformed so as to cover each pixel. Here, the patterns of the writingtransistors 1A or the driving transistors 1B of the RGB pixels areasymmetric to one another. However, the anode electrodes AD are formedto be symmetric for allowing the aperture ratio of the organic ELelement 1D to be uniform. Accordingly, below the anode electrode AD-G ofthe G (green) pixel, a part of the auxiliary capacitor 1J of the B(blue) pixel is disposed. In addition, an area denoted by diagonal linesin the figure forms a parallel plate capacitor that is configured by theanode electrode AD-G of the G (green) pixel and an upper electrode ofthe auxiliary capacitor 1J of the B (blue) pixel.

FIG. 11 is a schematic cross-sectional view taken along line A-A shownin FIG. 10. In the auxiliary capacitor 1J of the B (blue) pixel, acathode 1H is set in a first metal wiring that becomes a lower electrodeD1, and a source s of the driving transistor 1B, that is, an anode isset in polysilicon that becomes an upper electrode D2. As a result, theanode of the G (green) pixel and the anode of the B (blue) pixelconfigure a parallel plate, whereby parasitic capacitance Cp is formed.

Circuit Diagram Illustrating Parasitic Capacitance

FIG. 12 is a circuit diagram illustrating the parasitic capacitance. Thesignal line DTL is connected to the writing transistor 1A, and thesource electrode or the drain electrode of the writing transistor 1A isconnected to the gate electrode (node g) of the driving transistor 1B.

To the drain electrode of the driving transistor 1B, the power supplyline DSL is connected, and the holding capacitor 1C is connected betweenthe gate electrode and the source electrode. The source electrode(source s) of the driving transistor 1B is connected to the anodeelectrode of the organic EL element 1D. Between the anode electrode andthe cathode electrode (cathode 1H) of the organic EL element 1D, theauxiliary capacitor 1J is connected. In addition, between the anodeelectrode and the cathode electrode of the organic EL element 1D,parasitic capacitance 1I of the organic EL element 1D is configured.

As described above, since the auxiliary capacitor 1J of the B (blue)pixel is set in the area of the G (green) pixel, parasitic capacitanceCp is formed between the anode of the G (green) pixel and the upperelectrode (anode) of the auxiliary capacitor 1J of the B (blue) pixel.

Timing Chart

FIGS. 13A and 13B are timing charts illustrating the operation performedduring a sampling period of a video signal and a mobility correctingperiod. Here, a change in the emission luminance of the G (green) pixeldue to a difference in a sampling electric potential (emissionluminance) of the B (blue) pixel will be described.

FIG. 13A represents the appearance of a change in the electric potentialin a case where a same video signal electric potential Vsig is writteninto the G pixel and the B pixel so as to be in a same driving state.When the same video signal electric potential Vsig is written, a rise inthe electric potential of the source s of the driving transistor 1B ofthe G pixel, that is, the anode due to capacitive coupling, which occursat the time when the video signal is written, can be represented as thefollowing Expression (1).

(Vsig−Vo)×Cs/(Cs+Coled_(—) G+Csub_(—) G)  (1)

Accordingly, the rise in the electric potential of the source of thedriving transistor 1B of the G pixel is not influenced by the parasiticcapacitance Cp.

FIG. 13B represents a state in which the video signal electric potentialVsig that is the same as that represented in FIG. 13A is written intothe G pixel, and a video signal electric potential Vsig0 is written inthe B pixel. Here, it is assumed that Vsig>>Vsig0 and Vsig0 is a grayscale representing a color close to black. When these video signalelectric potentials are written into the pixels, a rise in the electricpotential of the source s of the N-type driving transistor 1B of the Gpixel, that is, the anode due to capacitive coupling, which occurs atthe time when the video signals are written, can be represented as thefollowing Expression (2).

(Vsig−Vo)×Cs/(Cs+Coled_(—) G+Csub_(—) G+Cp)  (2)

Accordingly, the rise in the electric potential of the source of theN-type driving transistor 1B of the G pixel is influenced by theparasitic capacitance Cp.

As a result, the relation of “Expression (1)”>“Expression (2)” issatisfied. Thus, in a case where the B pixel located adjacent to the Gpixel has a high gray scale, the gate-to-source voltage of the drivingtransistor 1B decreases so as to decrease the luminance when the videosignal is written. As described above, when anodes of adjacent pixelsform parasitic capacitance, there is influence of one pixel on the otherpixel.

In this embodiment, the influence of a change in the video signalelectric potential of one pixel of adjacent pixels on the luminance ofthe other pixel due to formation of parasitic capacitance between anodesof the adjacent pixels, as described above, can be prevented.

3. Configuration Example of this Embodiment System Configuration

FIG. 14 is a diagram of the system configuration representing oneexample of this embodiment. As represented in FIG. 14, an organic ELdisplay device 100 has a configuration including a pixel array unit 102formed by two-dimensionally disposing pixels (PXLC) 101 in a matrixshape and a driving unit that is disposed on the periphery of the pixelarray unit 102 and drives each pixel 101. As the driving unit thatdrives the pixels 101, for example, a horizontal driving circuit 103, awriting scanning circuit 104, and a power supply scanning circuit 105are disposed.

In the pixel array unit 102, in the pixel array of m rows and n columns,scanning lines WSL-1 to WSL-m and power supply lines DSL-1 to DSL-m arewired for each pixel row, and signal lines DTL-1 to DTL-n are wired foreach pixel column. The configuration of these components is the same asthat represented in FIG. 1.

Pixel Structure First Example

FIG. 15 is a schematic plan view illustrating an example (first example)of a pixel structure according to this embodiment. FIG. 15 representsthe disposition configuration of an R (red) pixel, a G (green) pixel,and a B (blue) pixel. Each pixel is configured between the power supplyline DSL and the scanning line WSL that extend in the horizontaldirection (horizontal direction in the figure), and areas of the RGBpixels are partitioned by signal lines DTL that extend in the verticaldirection (the vertical direction in the figure).

Within the area of each pixel, a writing transistor 1A, a drivingtransistor 1B, and a holding capacitor 1C are disposed. In addition, anauxiliary capacitor 1J that is used for adjusting a writing gain or amobility correcting time is also disposed.

In the example represented in FIG. 15, a case is shown where the patterndensity of the G (green) pixel is lower than that of the R (red) pixel,and the pattern density of the B (blue) pixel is higher than that of theR (red) pixel.

In this layout, the B (blue) pixel having a high pixel density isdisposed so as to be reversed in the horizontal direction with respectto the layout of the R (red) pixel and the G (green) pixel in thefigure. Accordingly, in an area between the B (blue) pixel and the G(green) pixel, a signal line ETL-B is not disposed, and the auxiliarycapacitor 1J of the B (blue) pixel is set in from the above-describedarea to the area of the G (green) pixel. In addition, the anodeelectrode AD is denoted by a thick solid line in the figure and isformed so as to cover each pixel.

Here, the patterns of the writing transistors 1A or the drivingtransistors 1B of the RGB pixels are asymmetric to one another. However,the anode electrodes AD are formed to be symmetric for allowing theaperture ratio of the organic EL element 1D to be uniform. Accordingly,below the anode electrode AD-G of the G (green) pixel, a part of theauxiliary capacitor 1J of the B (blue) pixel is disposed.

In this embodiment, an upper electrode, which is disposed on the organicEL element side, of electrodes of one pair configuring the auxiliarycapacitor 1J of the B (blue) pixel is wired so as to be conductive withthe cathode electrode of the organic EL element. Accordingly, of theelectrodes of the auxiliary capacitor 1J of the B (blue) pixel, theupper electrode has an electric potential of the cathode electricpotential, and the lower electrode has an electric potential of theanode electric potential. In other words, the upper electrode having theelectric potential of the cathode electric potential is disposed betweenthe anode electric potential of the G (green) pixel and the anode (lowerelectrode) of the auxiliary capacitor 1J of the B (blue) pixel.Accordingly, due to a shield effect, formation of parasitic capacitancebetween the anode electrode of the G (green) pixel and the anode (lowerelectrode) of the auxiliary capacitor 1J of the B (blue) pixel isprevented.

FIG. 16 is a schematic cross-sectional view taken along line B-B shownin FIG. 15. In the pixel structure, an anode-side electrode (the lowerelectrode D1) of the auxiliary capacitor 1J that is conductive with thesource electrode (source s) of the driving transistor 1B that becomes afirst metal wiring is disposed on a glass substrate.

In addition, a cathode-side electrode (the upper electrode D2) of theauxiliary capacitor 1J is disposed on the lower electrode D1 through agate oxidation film. The upper electrode D1 is formed by polysiliconthat forms a middle layer between the first metal wiring and the secondmetal wiring (not shown).

On the upper electrode D1, an anode electrode AD-G of the G (Green)pixel and an anode electrode AD-B of the B (blue) pixel are disposedthrough an interlayer insulating film and a flattening film. On theanode electrodes AD-G and AD-B, a multi-layered film of the organic ELelement, not shown in the figure, is formed.

As described above, in this embodiment, the source s of the drivingtransistor 1B, that is, the anode is set in the first metal wiring thatbecomes the lower electrode D1 of the auxiliary capacitor 1J of the B(blue) pixel, and a cathode 1H is set in the polysilicon that becomesthe upper electrode D2. Accordingly, parasitic capacitance is notconfigured between the anode electrode AD-G of the G (green) pixel andthe anode (the lower electrode D1) of the B (blue) pixel.

In addition, the anode of the G (green) pixel and the upper electrode D2(cathode 1H) of the B (blue) pixel configure a parallel plate, wherebyparasitic capacitance CP is formed. However, the upper electrode D2 hasa fixed electric potential as the cathode 1H. Thus, even when anodeelectric potentials of the pixels change, there may be no influencethereof on the adjacent pixels. In other words, in each pixel, theemission luminance corresponding to the video signal electric potentialof the pixel can be acquired with being rarely influenced by changes inthe video signal electric potentials of adjacent pixels.

FIG. 17 is a schematic cross-sectional view taken along line C-C shownin FIG. 15. In this embodiment, the upper electrode D2 of the auxiliarycapacitor 1J is set as the cathode 1H, and the lower electrode D1 isconnected to the source s of the driving transistor 1B. Here, the lowerelectrode D1 is configured by a first metal wiring, and the source s ofthe driving transistor 1B is configured by polysilicon as a middlelayer. Accordingly, in order to allow these components to be conductivewith each other, contact holes are formed. In other words, a contacthole CH1 is formed in the lower electrode D2 of the auxiliary capacitor1J, and a contact hole CH2 is formed in the polysilicon as the source sof the driving transistor 1B, and these are made to be conductive toeach other by a second metal wiring.

Under the wiring structure described above, even when a configuration inwhich the auxiliary capacitor 1J of the B (blue) pixel is set in thearea of the G (green) pixel, formation of parasitic capacitance betweenthe anode electrode of the G (green) pixel and the electrode (lowerelectrode D1) of the anode electric potential of the auxiliary capacitor1J of the B (blue) pixel is suppressed.

Pixel Structure Second Example

FIG. 18 is a schematic cross-sectional view illustrating an example(second example) of a pixel structure according to this embodiment. Thisschematic cross-sectional view is a cross-sectional view taken alongline A-A shown in FIG. 15. In this pixel structure, the auxiliarycapacitor 1J of the B (blue) pixel is set in the area of the B (blue)pixel to the G (green) pixel. In addition, a shield electrode SD isdisposed between the auxiliary capacitor 1J and the anode electrode AD-Gof the G (green) pixel.

The lower electrode D1 of the auxiliary capacitor 1J of the B (blue)pixel is configured by the first metal wiring and is set as the cathode1H of the organic EL element. On the other hand, the upper electrode D2of the auxiliary capacitor 1J of the B (blue) pixel is configured bypolysilicon as a middle layer and is set as the source s of the drivingtransistor, that is, the anode of the organic EL element.

Under such a configuration, according to this embodiment, the shieldelectrode SD is disposed between the upper side of the upper electrodeD2 and the anode electrode AD-G of the G (green) pixel. Morespecifically, an interlayer insulating film is disposed on the upperelectrode D2 of the auxiliary capacitor 1J of the B (blue) pixel, andthe shield electrode SD is disposed on the interlayer insulating film.The shield electrode SD is configured as the second metal wiring and isconductive with the cathode 1H of the organic EL element.

On the shield electrode SD, the anode electrode AD-G of the G (green)pixel and the anode electrode AD-B of the B (blue) pixel are disposedthrough the flattening film. On the anode electrodes AD-G and AD-B, amulti-layered film of the organic EL element, not shown in the figure,is formed.

According to this embodiment formed by the above-describedconfiguration, the shield electrode SD, which is the same node as thecathode 1H, is interposed between the anode electrode AD-G of the G(green) pixel and the upper electrode D2 of the auxiliary capacitor 1Jof the B (blue) pixel. Accordingly, parasitic capacitance is not formedbetween the anode electrode AD-G of the G (green) pixel and the upperelectrode D2 of the auxiliary capacitor 1J of the B (blue) pixel. Inaddition, even in a case where parasitic capacitance Cp is formedbetween the anode electrode AD-G and the shield electrode SD, thecathode 1H has a fixed electric potential. Thus, even when the anodeelectric potentials of the pixels change, influence thereof on theadjacent pixels is rare. As a result, in each pixel, the emissionluminance corresponding to the video signal electric potential of thepixel can be acquired with being rarely influenced by changes in thevideo signal electric potentials of adjacent pixels.

In the above-described embodiment, a case where the present invention isapplied to an organic EL display device using an organic EL element asthe electro-optical element of the pixel 101 has been described as anexample. However, the present invention is not limited to such anapplication and may be applied to all the display devices that use anelectro-optical element (light emitting element) of the current-driventype in which the emission luminance changes in accordance with thevalue of a current flowing through the device.

4. Applications

The above-described display device according to this embodiment can beapplied to various electronic apparatuses by being disposed in a mainbody casing thereof. As examples, the above-described display device canbe applied to various electronic apparatuses shown in FIGS. 19 to 23.For example, the above-described display device can be used as a displaydevice of electronic apparatuses in all the fields, in which a videosignal input to the electronic apparatus or a video signal generated inthe electronic apparatus is displayed as an image or a video, such as adigital camera, a notebook personal computer, a mobile terminal deviceincluding a cellular phone and the like, and a video camera.

As described above, by using the display device according to thisembodiment as a display device of the electronic apparatuses in all thefields, the image quality of a display image can be improved.Accordingly, there is an advantage that a high-quality image display canbe performed in various electronic apparatuses.

In addition, the display device according to this embodiment includes adisplay device having a sealed configuration in a module shape. Forexample, a display module that is formed by being attached to anopposing portion of a pixel array unit 102 such as transparent glasscorresponds to such a display device. In the transparent opposingportion, a color filter, a protection film, or the like may be disposed,and the above-described light shield film may be additionally disposed.In addition, in the display module, a circuit unit used for input oroutput of a signal or the like to the pixel array unit from the outside,an FPC (flexible print circuit), or the like may be disposed.

Hereinafter, concrete examples of the electronic apparatus to which thedisplay device according to this embodiment applies will be described.

FIG. 19 is a perspective view showing the outer appearance of atelevision set to which this embodiment is applied. The television setaccording to this application includes a video display screen unit 107that is configured by a front panel 108, and a filter glass 109, and thelike. By using the display device according to this embodiment as thevideo display screen unit 107, the television set is configured.

FIGS. 20A and 20B are perspective views showing the outer appearance ofa digital camera to which this embodiment is applied. FIG. 20A is aperspective view viewed from the front side, and FIG. 20B is aperspective view viewed from the rear side. The digital camera accordingto this application includes a light emitting unit 111 for flash, adisplay unit 112, a menu switch 113, a shutter button 114, and the like.The digital camera is manufactured by using the display device accordingto this embodiment as the display unit 112.

FIG. 21 is a perspective view showing the outer appearance of a notebookpersonal computer to which this embodiment is applied. The notebookpersonal computer according to this application includes a keyboard 122that is operated when a text or the like is input to a main body 121, adisplay unit 123 that displays an image, and the like. The notebookpersonal computer is manufactured by using the display device accordingto this embodiment as the display unit 123.

FIG. 22 is a perspective view showing the outer appearance of a videocamera to which this embodiment is applied. The video camera accordingto this application includes a main body unit 131, a lens 132 disposedon a side facing the front side for photographing a subject, astart/stop switch 133 that is used for photographing, a display unit134, and the like. By using the display device according to thisembodiment as the display unit 134, the video camera is manufactured.

FIGS. 23A to 23G are diagrams showing the outer appearances of a mobileterminal device, to which this embodiment is applied, such as a cellularphone. FIG. 23A is a front view in an open state, FIG. 23B is a sideview thereof, FIG. 23C is a front view in a closed state, FIG. 23D is aleft side view, FIG. 23E is a right side view, FIG. 23F is a top view,and FIG. 23G is a bottom view. The cellular phone according to thisapplication includes an upper casing 141, a lower casing 142, aconnection portion (here, a hinge portion) 143, a display 144, a subdisplay 145, a picture light 146, a camera 147, and the like. By usingthe display device according to this embodiment as the display 144 orthe sub display 145, the cellular phone is manufactured.

The present application contains subject matter related to thatdisclosed in Japanese Priority Patent Application JP 2009-003201 filedin the Japan Patent Office on Jan. 9, 2009, the entire contents of whichis hereby incorporated by reference.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

What is claimed is:
 1. A display panel comprising a plurality of pixelsdisposed on a substrate, wherein each of the plurality of pixelsincludes: a light emitting element, and a capacitor; wherein thecapacitor of a first one of the plurality of pixels is partiallyoverlapped, in a direction orthogonal to the substrate, by respectivepixel areas of two of the plurality of pixels.
 2. The display panel ofclaim 1, wherein the capacitor of the first one of the plurality ofpixels is partially overlapped, in a direction orthogonal to thesubstrate, by respective first electrodes of the light emitting elementsof the two of the plurality of pixels.
 3. The display panel of claim 2,wherein the respective first electrodes of the light emitting elementsof the two of the plurality of pixels are anode electrodes.
 4. Thedisplay panel of claim 1, wherein the capacitor of the first one of theplurality of pixels is connected to a first electrode, which is an anodeelectrode, of the light emitting element thereof.
 5. The display panelof claim 4, wherein the capacitor of the first one of the plurality ofpixels is not connected to a first electrode, which is an anodeelectrode, of the light emitting element of any of the plurality ofpixels other than the one of the plurality of pixels.
 6. The displaypanel of claim 4, wherein the first one of the plurality of pixels isalso one of the two of the plurality of pixels whose respective pixelareas overlap the capacitor of the first one of the plurality of pixels.7. The display panel of claim 1, wherein a capacitance of the capacitorof the first one of the plurality of pixels is different from acapacitance of the capacitor of at least one other of the plurality ofpixels.
 8. The display panel of claim 1, wherein the first one of theplurality of pixels is a blue pixel.
 9. The display panel of claim 1,wherein one of the two of the plurality of pixels whose respective pixelareas overlap the capacitor of the first one of the plurality of pixelsis a blue pixel.
 10. The display panel of claim 9, wherein the other oneof the two of the plurality of pixels whose respective pixel areasoverlap the capacitor of the first one of the plurality of pixels is agreen pixel.
 11. The display panel of claim 9, wherein a capacitance ofthe capacitor of the blue pixel is larger than a capacitance of thecapacitor of the other one of the two of the plurality of pixels whoserespective pixel areas overlap the capacitor of the first one of theplurality of pixels.
 12. The display panel of claim 1, wherein each ofthe plurality of pixels further includes: a driving transistor, whichhas a first current electrode connected to the light emitting elementand to the capacitor and which is configured to supply a drive currentcorresponding to a voltage between the first current electrode and agate electrode thereof to the light emitting element, and a samplingtransistor configured to sample a video signal, wherein, for each of theplurality of pixels, a first electrode of the capacitor is connected toa first electrode of the light emitting element, which is an anodeelectrode.
 13. The display panel of claim 12, wherein, for each of theplurality of pixels, a second electrode of the capacitor is connected tothe gate electrode of the driving transistor and the capacitor isconfigured to store a potential corresponding to the video signalsampled by the sampling transistor.
 14. The display panel of claim 12,wherein, for each of the plurality of pixels, the first electrode of thecapacitor is disposed further from the first electrode of the lightemitting element than a second electrode of the capacitor.
 15. Thedisplay panel of claim 12, wherein, for each of the plurality of pixels,a second electrode of the capacitor is connected to a second electrodeof the light emitting element, which is a cathode electrode.
 16. Thedisplay panel of claim 1, wherein the plurality of pixels are groupedinto color image formation units, each comprising N≧3 ones of theplurality of pixels that each have a color different from that of theother pixels of the unit, each unit including at least a blue pixel, agreen pixel, and a red pixel, and wherein the two of the plurality ofpixels whose respective pixel areas overlap the capacitor of the firstone of the plurality of pixels are grouped in the same unit as the firstone of the plurality of pixels.
 17. The display panel of claim 16,wherein the first one of the plurality of pixels is a blue pixel. 18.The display panel of claim 16, wherein one of the two of the pluralityof pixels whose respective pixel areas overlap the capacitor of thefirst one of the plurality of pixels is a blue pixel.
 19. A method ofmanufacturing a display panel comprising forming a plurality of pixelson a substrate, wherein each of the plurality of pixels includes: alight emitting element, and a capacitor; and wherein the capacitor of afirst one of the plurality of pixels is at least partially overlapped,in a direction orthogonal to the substrate, by respective pixel areas oftwo of the plurality of pixels.
 20. A method of manufacturing a displaypanel comprising: providing a substrate; forming a plurality of pixelcircuits on the substrate, each of the plurality of pixel circuitsincluding a driving transistor, a sampling transistor, and a capacitor;and forming a plurality of light emitting elements on the plurality ofpixel circuits, the plurality of light emitting elements beingelectrically connected to respective ones of the plurality of pixelcircuits, wherein an anode electrode of the capacitor of one of theplurality of pixel circuits is disposed closer to the substrate than acathode electrode of the capacitor of the one of the plurality of pixelcircuits, and wherein a first one of the plurality of light emittingelements and a second one of the plurality of light emitting elementsare formed such that they both at least partially overlap, in adirection orthogonal to the substrate, the capacitor of the one of theplurality of pixel circuits.